簡介:
本文著重講述了如果用WM_COPYDATA消息來實現兩個進程之間傳遞數據.
進程之間通訊的幾種方法:
在Windows程序中，各個進程之間常常需要交換數據，進行數據通訊。常用的方法有
使用內存映射文件
通過共享內存DLL共享內存
使用SendMessage向另一進程發送WM_COPYDATA消息
比起前兩種的復雜實現來,WM_COPYDATA消息無疑是一種經濟實惠的一中方法.
WM_COPYDATA消息的主要目的是允許在進程間傳遞只讀數據。Windows在通過WM_COPYDATA消息傳遞期間，不提供繼承同步方式。SDK文檔推薦用戶使用SendMessage函數，接受方在數據拷貝完成前不返回，這樣發送方就不可能刪除和修改數據：
這個函數的原型及其要用到的結構如下:
SendMessage(hwnd,WM_COPYDATA,wParam,lParam);
其中,WM_COPYDATA對應的十六進制數為0x004A
wParam設置為包含數據的窗口的句柄。lParam指向一個COPYDATASTRUCT的結構：
typedef struct tagCOPYDATASTRUCT{
DWord dwData;//用戶定義數據
DWord cbData;//數據大小
PVOID lpData;//指向數據的指針
}COPYDATASTRUCT;
該結構用來定義用戶數據。
具體過程如下:
首先,在發送方,用FindWindow找到接受方的句柄,然後向接受方發送WM_COPYDATA消息.
接受方在DefWndProc事件中,來處理這條消息.由於中文編碼是兩個字節,所以傳遞中文時候字節長度要搞清楚.
代碼中有適量的解釋,大家請自己看吧.
具體代碼如下:
//---------------------------------------------------
//發送方:
//---------------------------------------------------
using System;
using System.Drawing;
using System.Collections;
using System.ComponentModel;
using System.Windows.Forms;
using System.Data;
using System.Runtime.InteropServices;
namespace WindowsFormGetMsg
{
public class Form1 : System.Windows.Forms.Form
{
private System.Windows.Forms.TextBox textBox1;
private System.ComponentModel.Container components = null;
const int WM_COPYDATA = 0x004A;
public Form1()
{
InitializeComponent();
}
protected override void Dispose( bool disposing )
{
if( disposing )
{
if (components != null)
{
components.Dispose();
}
}
base.Dispose( disposing );
}
#region Windows Form Designer generated code
private void InitializeComponent()
{
this.textBox1 = new System.Windows.Forms.TextBox();
this.SuspendLayout();
//
// textBox1
//
this.textBox1.Location = new System.Drawing.Point
(176, 32);
this.textBox1.Name = "textBox1";
this.textBox1.Size = new System.Drawing.Size(160,
21);
this.textBox1.TabIndex = 0;
this.textBox1.Text = "textBox1";
//
// Form1
//
this.AutoScaleBaseSize = new System.Drawing.Size(6,
14);
this.ClIEntSize = new System.Drawing.Size(432, 266);
this.Controls.AddRange(new
System.Windows.Forms.Control[] {
this.textBox1});
this.Name = "Form1";
this.Text = "接收方";
this.ResumeLayout(false);
}
#endregion
[STAThread]
static void Main()
{
Application.Run(new Form1());
}
protected override void DefWndProc(ref
System.Windows.Forms.Message m)
{
switch(m.Msg)
{
//接收自定義消息 USER，並顯示其參數
case WM_COPYDATA:
COPYDATASTRUCT mystr = new
COPYDATASTRUCT();
Type mytype = mystr.GetType();
mystr =(COPYDATASTRUCT)m.GetLParam(mytype);
this.textBox1.Text =mystr.lpData;
break;
default:
base.DefWndProc(ref m);
break;
}
}
}
[StructLayout(LayoutKind.Sequential)]
public struct COPYDATASTRUCT
{
public IntPtr dwData;
public int cbData;
[MarshalAs(UnmanagedType.LPStr)] public string lpData;
}
}
//---------------------------------------------------
//接受方
//---------------------------------------------------
using System;
using System.Drawing;
using System.Collections;
using System.ComponentModel;
using System.Windows.Forms;
using System.Data;
using System.Runtime.InteropServices;
namespace WindowsFormGetMsg
{
public class Form1 : System.Windows.Forms.Form
{
private System.Windows.Forms.TextBox textBox1;
private System.ComponentModel.Container components = null;
const int WM_COPYDATA = 0x004A;
public Form1()
{
InitializeComponent();
}
protected override void Dispose( bool disposing )
{
if( disposing )
{
if (components != null)
{
components.Dispose();
}
}
base.Dispose( disposing );
}
#region Windows Form Designer generated code
private void InitializeComponent()
{
this.textBox1 = new System.Windows.Forms.TextBox();
this.SuspendLayout();
//
// textBox1
//
this.textBox1.Location = new System.Drawing.Point
(176, 32);
this.textBox1.Name = "textBox1";
this.textBox1.Size = new System.Drawing.Size(160,
21);
this.textBox1.TabIndex = 0;
this.textBox1.Text = "textBox1";
//
// Form1
//
this.AutoScaleBaseSize = new System.Drawing.Size(6,
14);
this.ClIEntSize = new System.Drawing.Size(432, 266);
this.Controls.AddRange(new
System.Windows.Forms.Control[] {
this.textBox1});
this.Name = "Form1";
this.Text = "接收方";
this.ResumeLayout(false);
}
#endregion
[STAThread]
static void Main()
{
Application.Run(new Form1());
}
protected override void DefWndProc(ref
System.Windows.Forms.Message m)
{
switch(m.Msg)
{
//接收自定義消息 USER，並顯示其參數
case WM_COPYDATA:
COPYDATASTRUCT mystr = new
COPYDATASTRUCT();
Type mytype = mystr.GetType();
mystr =(COPYDATASTRUCT)m.GetLParam(mytype);
this.textBox1.Text =mystr.lpData;
break;
default:
base.DefWndProc(ref m);
break;
}
}
}
[StructLayout(LayoutKind.Sequential)]
public struct COPYDATASTRUCT
{
public IntPtr dwData;
public int cbData;
[MarshalAs(UnmanagedType.LPStr)] public string lpData;
}
}
